Compositions and methods for inhibiting expression of a mutant gene

Abstract

The present invention relates to a double-stranded ribonucleic acid (dsRNA) for inhibiting the expression of a mutant gene, comprising a complementary RNA strand having a complementary region that is substantially complementary to a portion of the mutant gene, and which is partially complementary to the corresponding wild-type gene. The invention further relates to a pharmaceutical composition comprising the dsRNA and a pharmaceutically acceptable carrier. The pharmaceutical compositions are useful for inhibiting the expression of a target mutant gene, as well as for treating diseases caused by expression of the target gene. The invention also relates to methods for inhibiting the expression of a target mutant gene, as well as methods for treating diseases caused by the expression of the target gene.

1. A method for inhibiting the expression of a mutant target gene in a mammalian cell in vitro, comprising the steps of:
 a) introducing into said cell in vitro an oligoribonucleotide having a double stranded structure (dsRNA) consisting of two separate non-linked RNA strands,
 wherein a first strand of the dsRNA has a complementary region that is substantially complementary to less than 26 contiguous nucleotides of an RNA transcript of at least part of said target mutant gene and a second strand of the dsRNA is complementary to the first strand, and 
 
 b) maintaining the cell produced in step (a) for a time sufficient to obtain degradation of an RNA transcript of said mutant target gene, thereby inhibiting the expression of said target mutant gene in said cell without inhibiting expression of a wild-type form of the target gene,
 wherein said first and second strand of said dsRNA are 19 to less than 30 nucleotides in length, and 
 wherein the complementary region of said first strand of said dsRNA contains one mismatch relative to said mutant target gene and at least two mismatches relative to the wild type form of the target gene. 
 
 
     
     
       2. The method of  claim 1 , wherein said first and second strand of said dsRNA are 19 to 24 nucleotides in length. 
     
     
       3. The method of  claim 1 , wherein the second strand of said dsRNA is from 1 to 4 nucleotides longer than the first strand such that said dsRNA has a 1-4 nucleotide single stranded region at either the 5′ or 3′ end of said second strand. 
     
     
       4. The method of  claim 1 , wherein the second strand of said dsRNA is from 1 to 4 nucleotides longer than the first strand such that said dsRNA has a 1-4 nucleotide single stranded region at 3′ end of said second strand. 
     
     
       5. The method of  claim 1 , wherein the second strand of said dsRNA is from 1 to 2 nucleotides longer than the first strand such that said dsRNA has a 1-2 nucleotide single stranded region at either the 5′ or 3′ end of said second strand. 
     
     
       6. The method of  claim 1 , wherein the second strand of said dsRNA is from 1 to 2 nucleotides longer than the first strand such that said dsRNA has a 1-2 nucleotide single stranded region at 3′ end of said second strand. 
     
     
       7. The method of  claim 1 , wherein the said mutant gene is an oncogene.